二種類の高温ガス炉用不純ヘリウム中における Ni 基耐熱合金のクリープ破断特性

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In order to investigate the effect of impure helium environments of HTGR (high temperature gas-cooled reactor) on the creep rupture properties of heat resistant alloys for intermediate heat exchanger tubes, a creep rupture test has been carried out on four nickel-base superalloys in two impure helium gases, He-2 and PNP-He, at 1000℃. All the alloys were decarburized in some extent in PNP-He, while some of them were carburized in He-2 during the creep rupture testing, indicating that carbon potential of the gases was lower in PNP-He than in He-2 at 1000℃. The alloy hardened by γ′(Ni_3(Al, Ti)) precipitation, R4286, was suffered from the environmental effects resulting in the formations of γ′depleted zone, Al internal oxides and grain boundary carbide depleted zone beneath the alloy surface. The creep rupture life of this alloy in PNP-He was found to be one-third of that in He-2, which was mainly caused by the formation of carbide depleted zone along grain boundaries due to decarburization in PNP-He. The alloy hardened by α-W precipitation, KSN and 113MA, was suffered from the environmental effects resulting in the formations of α-W and grain boundary carbide depleted zones. The creep rupture life of KSN containing highest concentration of tungsten, 26%W, were found to be almost the same in the two environments, although this alloy was remarkably decarburized in PNP-He. Because KSN was mainly hardened by very fine precipitates of α-W, it was considered that the creep rupture life was little affected by decarburization. The alloy SZ was hardly decarburized in PNP-He, showing a good resistance to corrosion.
社団法人日本鉄鋼協会の論文
1982-12-01

二種類の高温ガス炉用不純ヘリウム中における Ni 基耐熱合金のクリープ破断特性

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